You mean modern apps. When you say, store apps, it sounds like you are talking about just the store. I would still suggest you attempt to reinstall the store and be sure your Windows Firewall Service is not disabled since that is strangely required (many apps will not run, including store, without it). If this is not the case, I would assume you either made some other change or had a bad upgrade. -- To be honest, a lot of folks found upgrading to the new fall update to be problematic (I was surprised this was the final version). I would suggest perhaps a clean install (I know, not the ideal solution, but what worked for me).